The present invention relates to a method and apparatus for monitoring, sampling or delivering a substance. More particularly, the invention is directed to a method and apparatus for applying tension to the skin of a patient to enhance the penetration of a penetrating device in a target site of a patient for monitoring, sampling or delivering.
Various devices have been proposed for monitoring, sampling and delivering substances transdermally. Although the prior subcutaneous delivery methods using a needle cannula for delivering pharmaceutical agents and drugs are effective for many applications, the pain normally induced by the needle cannula has prompted the development of less painful delivery methods. Transdermal delivery is one method of avoiding the pain caused by subcutaneous sampling and delivery using a needle cannula.
In recent years there has been an increased interest in microneedles for the sampling of components and for the transdermal delivery of drugs and other substances. Microneedles are micron size needles that can pierce the skin to a depth where a substance can be delivered into the epidermis so that the substance can be absorbed by the body. An advantage of the use of microneedles is the ability to penetrate the outermost layers of the skin with only minor discomfort to the patient compared to a standard needle.
The skin is made up of several layers with the upper composite layer being the epithelial layer. The outermost layer of the skin is the stratum corneum, which has well known barrier properties to prevent molecules and various substances, including most pharmaceutical agents, from entering the body and analytes from exiting the body. The stratum corneum is a complex structure of compacted keratinized cell remnants having a thickness of about 10-30 microns.
Various methods of delivering drugs through the skin form micropores or cuts through the stratum corneum. By penetrating the stratum corneum and delivering the drug to the skin in or below the stratum corneum, many drugs can be effectively administered. The devices for penetrating the stratum corneum generally include a plurality of micron size needles or blades having a length to penetrate the stratum corneum without passing completely through the epidermis. Examples of these devices are disclosed in U.S. Pat. No. 5,879,326 to Godshall et al.; U.S. Pat. No. 5,250,023 to Lee et al., and WO 97/48440.
Microneedles have been used with some success for various substances that are effective when delivered transdermally or intradermally. However, many of the prior microneedle devices that are currently available are not able to penetrate the skin uniformly across the microneedle surface thereby reducing the surface area available for delivery of the substance. The skin is generally elastic so that the skin deforms before the microneedles penetrate the skin. In some instances, the microneedles deform the skin but do not penetrate the skin to a depth sufficient to deliver a drug. Accordingly, there is a continuing need for improved microneedle devices.
Numerous methods and devices have been proposed to enhance the permeability of the skin and to increase the diffusion of various drugs through the skin so that the drugs can be utilized by the body. Typically, the delivery of drugs through the skin is enhanced by either increasing the permeability of the skin or increasing the force or energy used to direct the drug through the skin.
Sonic, and particularly ultrasonic energy, has been used to increase the diffusion of drugs through the skin. The sonic energy is typically generated by passing an electrical current through a piezoelectric crystal or other suitable electromechanical device. Although numerous efforts to enhance drug delivery using sonic energy have been proposed, the results generally show a low rate of drug delivery.
The prior methods and apparatus for the transdermal administration of drugs have exhibited limited success. Accordingly, a continuing need exists in the industry for an improved device for monitoring, sampling or delivering substances.
The present invention is directed to a method and apparatus for enhancing the penetration of a penetrating device into the skin of a patient. In particular, the invention is directed to a method and apparatus for uniformly penetrating a target site of a patient for sampling, detecting or monitoring a substance in the target site or delivering a substance to the target site.
A primary object of the invention is to provide a device capable of applying tension to a target area of the skin of a patient during the penetration by a penetrating device and during the delivery, monitoring, or sampling of a substance in the target area.
Another object of the invention is to provide a medical device for stretching the skin outwardly from a target area to enable a penetrating device to penetrate the target area with less deforming of the skin by the penetrating device.
Still another object of the invention is to provide a device for enhancing the penetration of a penetrating device to deliver a pharmaceutical agent to a target area of the stratum corneum of the skin to a sufficient depth where the pharmaceutical agent can be absorbed and utilized by the body.
A further object of the invention is to provide a medical device having an array of solid or hollow needles, microtubes, blades or lancets and a skin stretching device that cooperate together to enhance the penetration of the needles, blades or lancets to a substantially uniform depth in the skin.
Another object of the invention is to provide a medical device having a cavity for receiving a substance and having a plurality of needles, blades or lancets for penetrating the stratum comeum in a target area of the skin to a substantially uniform depth for delivering the substance to the skin.
A further object of the invention is to provide a device having a substantially conical shaped shield made of a flexible material that is able to stretch the skin of a patient outwardly from a target site when the device is pressed downward onto the skin of the patient.
Another object of the invention is to provide a medical device having a conical shaped shield that is able to apply a tension to the skin and enable a substantially uniform penetration of the skin by a penetrating device.
A further object of the invention is to provide a medical device for monitoring, sampling or delivering a substance where the device includes at least two arms that extend outwardly from a housing to contact and push the skin of a patient outwardly from a target area by applying a downward pressure on the device.
A still further object of the invention is to provide a medical device having a plurality of microneedles for penetrating the stratum corneum and a device for holding a target area of the skin under tension to enable uniform penetration of the skin by the microneedles.
These and other objects of the invention are substantially attained by providing a device for stretching the surface of the skin of a patient. The device comprises a medical device for contacting the skin of a patient, and a skin stretching device which is coupled to the medical device for stretching skin of a patient away from the medical device when a downward pressure is applied on the medical device toward the skin of a patient either before or after the medical device contacts the skin.
The objects and advantages of the invention are further attained by providing a delivery device for delivering a substance intradermally to a patient. The device comprises a housing having a top wall, a bottom wall and at least one side wall enclosing a cavity for containing a substance to be delivered to a patient, and at least one skin penetrating device on the bottom wall. The bottom wall has at least one opening for supplying the substance from the cavity to the at least one skin penetrating device. A stretching device is coupled to the housing for stretching the skin of a patient in at least one dimension. The stretching device has at least one member with a first end coupled to the device and a second end spaced axially from the at least one skin stretching device and the housing, wherein the at least one member is positioned to contact the skin of a patient in at least one dimension before the skin penetrating device contacts the skin.
Another object of the invention is to provide a method of subjecting the skin of a patient to a medical device. The method comprises the steps of providing a medical device having a skin stretching device, positioning the medical device with the stretching device on the skin of a patient and applying a sufficient force on the device toward the skin where the stretching device stretches the skin away from the medical device and the medical device contacts the skin.
The objects, advantages and other salient features of the invention will become apparent from the following detailed description which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the invention.